With the rapid development of semiconductor manufacturing technologies, semiconductor devices have been developed toward higher device density and higher integration level. Transistors have been widely used as the basic semiconductor devices. With the continuous increase of the device density and the integration level of the semiconductor devices, the gate sizes of the planar transistors have been continuously reduced. Accordingly, the control ability of the conventional planar transistors to their channel regions has become weaker and weaker. Thus, the short channel effect is generated; and the leakage current is increased. As a result, the electrical properties of the semiconductor devices are adversely affected.
To further reduce the sizes of the metal-oxide-semiconductor field-effect transistors (MOSFETs), multiple-gate field-effect transistors have been developed so as to increase the control ability of the gates of the MOSFETs; and reduce the short channel effect. Fin field-effect transistors (FinFETs) are a typical type of multiple-gate transistors. In an FinFET, the ultra-thin members (fins) can be controlled from at least two sides. Thus, comparing with the planar MOSFET, the control ability to the channel region is significantly enhanced; and the short channel effect is efficiently reduced. Further, comparing with other devices, FinFETs have a better compatibility with the existing fabrication technologies of the integrated circuits (ICs).
However, it is still desirable to enhance the performance of the FinFETs. The disclosed methods and semiconductor structures are directed to solve one or more problems set forth above and other problems in the art.